Fix Device::availableMemory crash on Vulkan 1.0 instances

[mbait]

Description

Device::availableMemory() unconditionally calls vkGetPhysicalDeviceMemoryProperties2 with a chained VkPhysicalDeviceMemoryBudgetPropertiesEXT. Both have preconditions that are never checked:

• vkGetPhysicalDeviceMemoryProperties2 requires Vulkan 1.1 (or VK_KHR_get_physical_device_properties2, promoted to core in 1.1).
• VkPhysicalDeviceMemoryBudgetPropertiesEXT requires the VK_EXT_memory_budget device extension.

When a VSG application creates a vsg::Instance with VK_API_VERSION_1_0 (still the default of vsg::Instance::create), this function dispatches an unresolved entry point and feeds the driver a struct it never advertised support for. Behaviour is undefined. On Mesa Lavapipe it segfaults inside a driver worker thread during normal scene compilation (MemoryBufferPools::reserveBuffer -> Device::availableMemory). The Khronos validation layer flags it as:

vkGetPhysicalDeviceMemoryProperties2(): Attempted to call with an effective API version of 1.0.0 … but this API was not promoted until version 1.1.0.

Fix

Gate the 1.1 path on both supportsApiVersion(VK_API_VERSION_1_1) and supportsDeviceExtension(VK_EXT_MEMORY_BUDGET_EXTENSION_NAME). When either is missing, fall back to the Vulkan 1.0 vkGetPhysicalDeviceMemoryProperties and treat memoryHeaps[i].size as the budget with zero live usage. The fallback returns a conservative upper bound — buffer pool sizing degrades gracefully instead of crashing.

No public API changes. The 1.1 + extension code path is unchanged for users who request it.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Reproduced and verified on Mesa 25.2.8 Lavapipe (lvp_icd.json) in a GPU-less Linux container with a minimal headless VSG application (vsg::Instance::create(..., VK_API_VERSION_1_0), offscreen framebuffer, one Builder::createSphere frame).

• Before the patch: SIGSEGV inside libvulkan_lvp.so during viewer->compile(), validation layer reports the API-version violation above.
• After the patch: clean run, no validation errors, expected image written.

Test Configuration:

• OS: Ubuntu 24.04 (LXC container, no GPU)
• Vulkan loader: 1.3.275
• Driver: Mesa 25.2.8 Lavapipe (LLVM 20.1.2)
• Compiler: GCC 13.3.0

Checklist

• My code follows the style guidelines of this project (clang-format clean)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings